Design and Scale-Up of Zero-Gap AEM Water Electrolysers for Hydrogen Production

Abstract

The design of a 10 cm2 (3.4 cm by 3.4 cm) and a 100 cm2 (10 cm by 10 cm) anion exchange membrane (AEM) water electrolyser cell for hydrogen production are described. The AEM cells are based on a zero-gap configuration where the AEM is sandwiched between the anode and cathode so as to minimise voltage drop between the electrodes. Nonprecious nickel-based metal alloy and metal oxide catalysts were employed. Various experiments were carried out to understand the effects of operating parameters such as current densities, electrolyte concentrations, and testing regimes on the performance of both 10 cm2 and 100 cm2 AEM electrolyser cells. Increasing electrolyte concentration was seen to result in reductions in overpotentials which were proportional to current applied, whilst the use of catalysts improved performance consistently over the range of current densities tested. Extended galvanostatic and intermittent tests were demonstrated on both 10 cm2 and 100 cm2 cells, with higher voltage efficiencies achieved with the use of electrocatalysts. Stability tests in the 100 cm2 AEM electrolyser cell assembled with catalyst-coated electrodes demonstrated that the cell voltages remained stable at 2.03 V and 2.17 V during 72 h operation in 4 M KOH and 1 M KOH electrolyte, respectively, at a current density of 0.3 A cm−2 at 323 K. The inclusion of cycling load tests in testing protocols is emphasized for rational evaluation of cell performance as this was observed to speed up the rate of degradation mechanisms such as membrane degradation.